–Three years after he was entombed in the rubble of the World Trade Center, New York City firefighter Jay Jonas worries that Americans have forgotten that the country is vulnerable to attack. "The biggest lesson? Don’t fall asleep," said Jonas, who flew into Des Moines Wednesday and will give an insiders' account of Sept. 11 at a public lecture tonight in Newton. "Make no mistake about it. This is a serious group of people. They want to destroy us."

Jonas, a battalion chief who led one of the first fire crews into the World Trade Center, recently studied Al-Qaida and other Muslim extremist groups during a 14-week counter-terrorism course at the U.S. Military Academy. "All is not well," said Jonas, 46, of Goshen, N.Y. "None of us are going to be safe for a very long time. This is not a war that’s going to be over in a couple years." With major cities tightening security, terrorists may go for "softer targets," Jonas said.

"As we’re driving in from the airport, I’m thinking, there's a target . . . and there's a target," he said. "It can be something much less conspicuous than a high-rise building in a big city." Jonas declined to identify the potential targets, saying it would be inappropriate to do so. On Sept. 11, 2001, Jonas was awaiting orders in the lobby of the north tower as a raging fire consumed 20 floors – each an acre in size – 100 stories above him. He saw a black shadow cross the floor. The second plane hit the south tower with a violent explosion.

"That radically changed things," said Jonas, who was then captain of Ladder Company 6 in Manhattan's Chinatown neighborhood. "That naivete disappeared. We knew we were under attack. One of the firemen said, 'I don’t know if we’ll make it through today.'" It occurred to Jonas then that terrorists had actually declared war on the United States when they bombed the twin towers in 1993. "We just didn’t do anything" then, he said. Jonas gave his crew of five firefighters their orders: Stick together, walk up 80 flights and help anyone you can.

"Without hesitation, they all said, 'OK, Cap, let's go. We’re with you,' " he said. As they hit the stairs, Jonas wondered if the U.S. Air Force would be protecting the building from the air. "I've never been to a fire where I was wondering if we had military backup," he said. Jonas was on the 27th floor, waiting for two firefighters to catch up, when an earthquake-like rumble shook the building and knocked out the lights. The south tower had just collapsed.

"I couldn’t believe it," Jonas said. A 22-year firefighter with two college degrees, he knew no U.S. high-rise had ever collapsed from fire. He looked at his firefighters for a moment, then said, "If that tower can go, this one can go. It's time for us to get out of here." Still, Jonas was nervous because he hadn't gotten an order to evacuate. He later learned the order was radioed before the south tower fell, but he couldn't hear it – probably because the repeaters, which boost radio signals so they can be heard inside skyscrapers, weren't working.

On the way down, they passed a firefighter Jonas used to carpool with to work, Lt. Mike Warchola, who was helping a civilian suffering from chest pain. "Mike, come on," Jonas told him. "Let's go." "We'll be right behind you," Warchola told him. Around the 20th floor, the firefighters found an injured woman in a doorway crying. Helping Josephine Harris, 59, limp down the stairs slowed their descent and bottlenecked everybody behind them. "This was the terrifying time," Jonas said. "The spooky music in this whole scenario is that the clock is ticking. Instead of descending with a normal gait, it was: Step. Step. Step. It was like water torture."

By the fourth floor, Jonas felt a twinge of confidence. They could make it, he thought. Then Harris' legs gave way. She could no longer walk. Jonas broke into the fourth floor to find a chair in which to carry Harris. "It's the biggest office building in the world, and this is not an office floor," he said. "It's a mechanical equipment floor." He searched, running to the opposite side of the building, but couldn't find a chair." Something told me, 'This isn't working out. I've got to get back to the stairway. We're just going to have to drag her.' "

About four feet from the door, there was a thunderous roar and the floor bucked like ocean waves. The collapse had started. Jonas pulled the door handle, but the compression effect kept it stuck shut. He yanked again. It opened. He dove into the stairway, curled into a ball, and waited to be crushed, he said. Rushing wind picked up one of his firefighters and threw him down two flights of stairs. Debris pummeled them, cutting and bruising their skin. Each time a floor pancaked onto the one below, the tremendous vibration bounced them like basketballs. Steel twisted around them with an ear-splitting screech.

"It's over," he thought. "This is how it ends." Then it stopped – 110 floors flattened in 13 seconds. Gagging and coughing in a cloud of dust, Jonas did a roll call. Of the 13 people with him – 11 firefighters, a Port Authority police officer and Harris – one had a concussion, one had a separated shoulder and one possibly had broken ribs. But for the most part, they were fine. Maydays crackled over the radio from elsewhere in the tower. Warchola, the firefighter they'd passed as he helped a civilian, radioed that he was in the B stairway on the 12th floor, badly hurt.

Jonas tried to reach him, but chunks of the stairway were missing or blocked with debris. They were trapped in a two-story pocket. A second mayday came from Warchola. Then a third. Jonas took a breath. "I'm sorry, Mike," he said into the radio. "I can’t help you." The firefighters could hear fires crackling around them. They found a toilet on the fifth floor that wouldn't flush, but would be handy if someone needed to use the john. They found some sprinkler piping they could break into when they got thirsty. They found a service elevator with an open shaft below and figured that, if desperate, they could rappel down into a subcellar and find a subway tunnel out. They found a can of orange soda and shared sips.

An hour passed. Then two hours. Rescuers repeatedly asked for their location. Over and over Jonas said, "North tower, B stairwell, fourth floor." At one point, he heard a firefighter on the radio say, "Where's the north tower?" "I'm thinking, 'You hayseeds. It's the big building on the corner,' " Jonas said. He was unaware that all the physical landmarks of the World Trade Center had disappeared. After 31/2 hours, the dust cleared and a ray of light beamed through a small hole.

"Guys," Jonas told his crew. "There used to be 106 floors above us, and now I'm seeing sunshine. "By widening the hole, they were able to use ropes to climb out. The view stunned them: 16 acres of rubble and two buildings ablaze just feet away. As they hiked over the treacherous debris, Jonas was optimistic he'd see other survivors emerging. "We had a nice little pocket. There’s got to be hundreds of them," he thought. To Jonas’ shock, only his group of 14 and four others escaped the wreckage alive.

The rescue personnel death toll: 421. Altogether, about 3,000 people were confirmed dead in the Sept. 11 terrorist attacks. "The numbers are kind of cold," Jonas said Wednesday. "I hope my story gives this a personal feeling. People aren't recognizing how significant a day it really was."